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April 1994

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1994.04.07 14:05 "", by Christoph Wissing
1994.04.07 17:50 "6 Bit TIFF", by Niles Ritter
1994.04.08 09:48 "", by Karsten Spang

1994.04.07 14:05 "", by Christoph Wissing


At first congratulations to your good software, the libtiff.
I`m using it within my "Diplomarbeit" for reading and writing pictures.

I encountered a problem when reading some grayscale X-Ray-Images:
They use 6 Bit per Sample, and I`ve seen in your doc`s:
    o Class G for grayscale images
	SamplesPerPixel = 1
	BitsPerSample = 4, 8
	Compression = 1 (none) 5 (LZW)
	PhotometricInterpretation = 0 (Min-is-White), 1 (Min-is-Black)

so they are not supported, in spite of that palette color images with 6 Bit are.
I`ve proven that, when loading such a picture with the libtiff,
the pictures are nearly completely black, but not useable.
Are there plans to extend the libtiff to read 6 Bit graylevel images,
or should I try to work it into the libtiff? Or do I misunderstand
something? I`m using the libtiff version 3.2 on a Sun, a Linux PC, an SGI,
and an SCO-Unix PC and on my Atari Falcon: No where a problem with other
pictures, only these 6 Bit Bastards don`t work.
Have you any suggestions?
Of course I could send you such an 6 Bit (uncompressed!) Picture,
if you want. But, of course, I doon
don`t want to steal your time, only please let me know whether
I should do a workaround by myself, or I`ve misunderstood something,
or in the near future there is support for 6Bit Grayscales.

With many greetings,